Fixed E129 flake8 errors

visually indented line with same indent as next logical line

_pytest/_code/_py2traceback.py

@@ -30,7 +30,7 @@ def format_exception_only(etype, value):
     # would throw another exception and mask the original problem.
     if (isinstance(etype, BaseException) or
         isinstance(etype, types.InstanceType) or
-        etype is None or type(etype) is str):
+            etype is None or type(etype) is str):
         return [_format_final_exc_line(etype, value)]
 
     stype = etype.__name__